Dr., this pus filled pimple has been popping on&off same spot since 4-5 months now.. This is the third time it has become pus filled, first time the pus was drained on its own. We thought it may become fine, but it was still hard and pricky and a bit swelled like a bite. now again this has become like this. What ointment can we put and what could be the reason for this.